I have applied in a US university (let say it is A) in a natural science department for PhD admission. One weeks ago I emailed the graduate director to know my status because I received admission from another university. I wrote him that, I will not accept the other university's admission offer if I'm in their consideration pool. The graduate director emailed me back that I have received the admission. He also suggested me to sign the offer letter he sent me and to complete the admission within two weeks.
After carefully checking the email, I saw that I didn't get the offer letter in the attached file. I replied him back immediately regarding the missing attachment. I replied the professor two times regarding the missing attachment in the consequent two days but still I haven't received any reply. The admin and the graduate director are not responding whereas 7 days have been passed.
Somehow I had a connection with a current student who is studying (PhD) in that department and I requested him to talk with the admin. He discussed my matter with the admin who writes and handles the documents. The admin told him that, She didn't process any document for me regarding admission offer.
What should I do in this case? I have another admission offer from another university but I'm very much interested to the program I'm taking about.
EDIT: I'm an International Student
"A bird in the hand is worth two in the bush" - old proverb
In other words, a certain thing is worth much more than a possible thing. You have an opportunity to get into a school for certain. You should not waste that opportunity on a 'maybe'.